1. Field of the Invention
The present invention relates to blood oxygenating devices which are used during cardiac and lung surgery to remove dissolved carbon dioxide and introduce dissolved oxygen into the blood of an anesthetized patient undergoing surgery.
2. Description of the Prior Art
The advances of medical technology in recent years now allow surgeons to perform intricate cardiac and lung surgery not previously possible. Surgery can be performed in which the heart and lungs of a patient are temporarily disabled and do not perform their normal vital functions of removing carbon dioxide and providing oxygen to the patient's blood and pumping the blood through the body of the patient. During the interval that the heart and lungs do not perform these vital functions, some artificial means of providing oxygen to the blood of the patient and circulating the blood through the patient's body must be provided.
A number of conventional blood oxygenating devices are presently commercially available. Originally, blood oxygenators typically provided a heat exchanger in the arterial reservoir of blood. The arterial reservoir in a blood oxygenator contains the blood which has been reoxygenated and is ready for return to the patient's body. Typical among such blood oxygenators are the Bentley Q-100, manufactured by Bentley Laboratories, Irvine, Calif., and the Optiflo I oxygenator manufactured by Cobe Laboratories, Denver, Colo. The purpose of the heat exchanger is to maintain the blood at the body temperature of the patient as it is returned to the patient. However, certain technical difficulties arose with the placement of a heat exchanger in oxygenated blood. Specifically, the problem foreseen was that of generation of gaseous emboli caused by heating an oxygen rich solution such as blood, or more specifically plasma with oxygen and other gases dissolved therein. Such gaseous emboli could be quite dangerous to a patient if they are introduced into the arterial line returning blood to the patient. The likelihood of introduction of gaseous emboli into the patient is enhanced if the heat exchanger is placed in the arterial reservoir of blood to be returned to the patient.
Accordingly, blood oxygenators were developed in which the heat exchanger was moved to the venous side of the blood oxygenator to reduce the hazard of potential emboli and to increase the heat exchange efficiency. Commercial blood oxygenators of this type include the Shiley 100 A Oxygenator, manufactured by Shiley Laboratories of Irvine, Calif., the Bentley Spiraflo BOS-10 Blood Oxygenator manufactured by Bentley Laboratories, Inc., of Irvine, Calif., the Optiflo II Blood oxygenator and the D-750 Thermoflow Oxygenator, manufactured by Delta Medical Industries of Costa Mesa, Calif. However, by moving the heat exchanger to the venous or inlet side of the blood oxygenator, a degree of temperature control is lost, since the reoxygenated blood may remain in an arterial reservoir for a variable period of time prior to return to the patient.
Another problem which has existed in blood oxygenators is the limited efficiency of oxygen transfer which has heretofore been achieved. Oxygen transfer is effectuated by transforming the liquid blood from the venous inlet into a foam. This is achieved by the introduction of gaseous oxygen into the blood. As oxygen bubbles pass through the blood the blood is converted from a liquid to a foam. However, with conventional spargers which introduce oxygen into the blood, only a relatively slow rate of oxygen transfer has heretofore been achieved. As a consequence, a greater volume of blood is necessary for use during surgery since the rate of reoxygenation of blood is relatively slow.